Editing a movie is an art form in itself. Manipulating the timeline to tell a story makes films different from other visual art forms such as photography or painting. An important aspect of movie editing is setting up transitions between movie clips. This is especially true because transitions between clips have increased dramatically since the early days of cinema. Movie content today can easily have multiple cuts per second.
Telling a story through film requires control over shot sequences, scene transitions and special effects. Although current traditional digital movie editors provide many sophisticated tools, these tools do not easily extend to three dimensional (3D) movies. Stereoscopic or 3D cinema demands unique editing techniques because it is fundamentally different from a traditional film in that typically two images are viewed to create a perception of viewing a 3D scene. In stereoscopic video a person's eyes converge on an object, and the muscles that control that person's optics give absolute depth of the object. The person's brain has the ability to perceive depth from two images of the scene taken from slightly different viewpoints. This is known as fusion, since the brain perceives a single image of the scene with depth rather than “double vision”. Fusion occurs in a region of the brain known as Panum's area, giving relative depth around a point called the vergence point.
There are many challenges that are unique to the stereo movie setup. Stereo movies allow a viewer's eyes to wander about the scene, much like reality. Therefore, significant efforts must be taken to focus the audience's attention. If scene transitions are not designed carefully, fusion may break down between cuts as the audience takes time to adjust. There are also biological limits to what can be fused, and objects too close to the viewer will be perceived as double. Additionally, shots taken with a large camera baseline or with vertical disparity may cause headaches and discomfort. However, the potential to create a visually stunning experience in stereoscopic cinema outweighs the extra work needed to overcome these challenges. Stereo movies thrill audiences: cliffs bring real vertigo, monsters are close enough to touch and jewelry sparkles with head movement.